JP2008219272A - Fixed electrode unit and manufacturing method thereof, and electret condenser microphone unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixed electrode unit reduced in a stray capacity of a microphone, having a structure which can be incorporated in a unit case and is applicable to a large-diameter unit having many holes forming openings of a fixed electrode as a constituent member of an electret micrphone unit having respective members disposed by a pressing force by a folded-back portion of the unit case. <P>SOLUTION: The fixed electrode unit 10 has the fixed electrode 15 having an electret material 31 stuck on the surface opposed to a diaphragm 13, an insulating ring 32 having an opening that the fixed electrode enters and defining a radial size in the unit case to fix the fixed electrode at a predetermined position, and a fixing means of uniting the fixed electrode and an insulating ring so that the fixed electrode entering the opening portion of the insulating ring forms a plane at the same height as the insulating ring. Further, the fixed electrode has its external diameter D1 smaller than the internal diameter D2 of a diaphragm holder 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixed pole unit incorporated in a unit case as a constituent member of an electret condenser microphone unit and a manufacturing method thereof, and an electret condenser microphone unit including the fixed pole unit. The present invention relates to a technology that makes it possible to increase detection sensitivity by reducing stray capacity.

The condenser microphone includes a condenser microphone unit in which a diaphragm unit including a diaphragm that vibrates by sound waves and a fixed pole are disposed to face each other with a spacer interposed therebetween. A gap corresponding to the thickness of the spacer is formed between the diaphragm unit and the fixed pole to form a kind of capacitor. For this reason, when the diaphragm receives sound and vibrates, the capacitance between the diaphragm unit and the fixed pole changes according to the vibration, and this change in capacitance is output as an audio signal. Yes. Therefore, the microphone unit is configured by stacking the diaphragm unit and the fixed pole via the spacer.
One type of condenser microphone is an electret condenser microphone that uses an electret material for a fixed pole serving as a back pole. An electret material is a polymer compound that stores a charge semipermanently.

The electret condenser microphone unit has a structure as shown in FIG. 8, for example. FIG. 8 is a longitudinal sectional view showing an example of a conventional electret condenser microphone unit.
In FIG. 8, an electret condenser microphone unit (hereinafter referred to as “microphone unit”) 101 is configured by housing the following parts in a bottomed cylindrical unit case 111. In the unit case 111, a portion corresponding to the bottom portion is the front side, and serves as an audio input portion in the microphone. In addition, a plurality of holes 111a for introducing sound into the microphone unit are formed at the bottom. In the unit case 111, a ring-shaped diaphragm holder 112 is disposed at a position closest to the bottom, and a diaphragm 113 having an outer peripheral edge fixed to one end surface of the diaphragm holder 112 is disposed. Has been.

A fixed pole 115 is disposed opposite to the diaphragm 113 with a spacer 114 as a ring-shaped member interposed. The fixed electrode 115 is made of a metal disk as a base material, and, for example, an electret material 131 is attached to the surface facing the diaphragm 113 to constitute an electret board. The spacer 114 is made of a thin resin and is in close contact with the outer peripheral edge of the rear end surface (lower end surface in FIG. 8) of the diaphragm 113.
In the unit case 111, an insulating sleeve 116 as a fixed pole support is disposed on the rear surface side of the fixed pole 115. The insulating sleeve 116 is made of, for example, synthetic resin, and regulates the radial dimension in the unit case 111 to fix the fixed pole 115 at a predetermined position. The insulating sleeve 116 is bonded to the fixed electrode 115 with an adhesive, and the electret material 131 is attached to a flat portion formed by the insulating sleeve 116 and the fixed electrode 115.

  In FIG. 8, a conductive sleeve 117 made of a conductive material is inscribed on the inner peripheral surface of the insulating sleeve 116. The rear end surface portion of the conductive sleeve 117 is in contact with a circuit pattern (not shown) formed on the disc-shaped printed board 119. A folded portion 111 b of the open end edge of the unit case 111 is in contact with the peripheral edge of the rear end surface of the printed circuit board 119. The folded portion 111b presses the printed circuit board 119 forward (upward in FIG. 8), and the conductive sleeve 117 is pushed forward (upward in FIG. 8) by the pressing force generated by the folded portion 111b. ing. In addition, the fixed electrode 115 is pressed by this pressing force, and the diaphragm holder 112 is pressed against the bottom surface of the unit case 111 via the spacer 114, and the positions of these members in the unit case 111 are determined. Is fixed. The conductive sleeve 117 electrically connects the fixed pole 115 and the printed board 119. On the printed circuit board 119, a field effect transistor (hereinafter referred to as “FET”) 118 constituting an impedance converter is disposed. A part of the terminals of the FET 118 is connected to a predetermined circuit pattern of the printed circuit board 119 by soldering or the like.

However, in the microphone unit 101 having the structure described above, as shown in FIG. 9, the diameter (outer diameter) of the outer edge portion 115 a of the fixed pole 115 and the diameter (inner diameter) of the inner edge portion 112 a of the diaphragm support 112. There is an overlap x between the two. The electrostatic capacity of the overlapping portion x becomes a stray capacity, and the sensitivity as a microphone is reduced.
Therefore, in such a structure, if the aperture of the microphone unit is reduced, the ratio of effective capacity to stray capacity cannot be increased, resulting in a lossy microphone unit.

In view of this, several means have been proposed in which the generation of stray capacitance (floating capacitance) is prevented to increase detection sensitivity (see, for example, Patent Documents 1 and 2).
Both of the techniques described in Patent Documents 1 and 2 attempt to improve the sensitivity by reducing the stray capacity by setting the outer diameter of the fixed pole to be equal to or smaller than the inner diameter of the diaphragm support.

  However, in the technique described in Patent Document 1, a fixed pole and an insulating sleeve are integrally formed, and after an electret material is attached to the fixed pole, an opening is opened in the fixed pole. Therefore, although it is suitable for a small-diameter unit, for example, in order to apply to a large-diameter unit having a diameter of about 10 mm or more, it is necessary to increase the number of the openings. It was difficult.

The technique described in Patent Document 2 also has a structure in which a back electrode corresponding to a fixed electrode and an electret layer are formed on an insulating substrate, and is suitable for a small diameter unit, but is applied to a large diameter unit. It was difficult to process. In addition, the device described in Patent Document 2 is obtained by positioning the vibration film and the back electrode by the insulating substrate. Therefore, it cannot be easily applied to a structure in which each member is positioned by the pressing force by the folded portion of the unit case.
That is, in the microphone unit, it is known that the sensitivity is further increased as the distance between the vibrating membrane and the back electrode is closer. However, if the back electrode is formed in a convex shape on the insulating substrate, the distance between the diaphragm and the back electrode becomes too short, and the center part of the diaphragm is greatly bent and contacts the opposite center part of the back electrode. There is a possibility that the function as a microphone may be deteriorated. In this case, it is difficult to adjust the distance between the diaphragm and the back electrode depending on the thickness of the spacer, and the capacitance changes with the change of the spacer thickness, and the sensitivity decreases. There is also a risk that a lot of noise will occur.
Furthermore, in the above-mentioned Patent Document 1, since the back electrode is formed on the insulating substrate, there is a problem that the electrical conduction between the back electrode and the printed circuit board becomes a complicated structure.
Japanese Patent Application No. 2006-341718 JP 2003-78997 A

  The present invention has been made in view of the above circumstances, and can be incorporated into the unit case as a constituent member of an electret condenser microphone unit having a structure in which each member is positioned by the pressing force of the folded portion of the unit case. A fixed pole unit that can be applied to a large-diameter unit that has a large number of openings that can be opened in the fixed pole, can reduce the stray capacity of the microphone section, a manufacturing method thereof, and the fixed pole unit. An object is to provide an electret condenser microphone unit provided.

  The fixed pole unit according to the present invention is incorporated in a unit case, and is disposed to face the diaphragm stretched on the diaphragm holder with a gap, and constitutes a capacitor with the diaphragm. A fixed pole having an electret material pasted on the surface facing the diaphragm, and an opening into which the fixed pole enters, and defining a radial dimension in a unit case to define the fixed pole The fixed pole and the insulating ring are integrated so that the insulating ring for fixing the insulating ring at a predetermined position and the fixed pole entering the opening of the insulating ring form a plane having the same height as the insulating ring. Fixing means, wherein the fixed pole has an outer diameter that is equal to or smaller than an inner diameter of the diaphragm holder.

  A method of manufacturing a fixed pole unit according to the present invention is built in a unit case, and is disposed to face a diaphragm stretched on a diaphragm holder with a gap therebetween, thereby forming a capacitor with the diaphragm. A fixed pole on which an electret material is bonded to the surface facing the diaphragm, and an opening into which the fixed pole enters. The radial dimension in the unit case is defined to define the fixed pole An insulating ring fixed at a position, and fixing means for integrating the fixed pole and the insulating ring so that the fixed pole entering the opening of the insulating ring forms a plane having the same height as the insulating ring; The fixed pole is a method for manufacturing a fixed pole unit, the outer diameter of which is equal to or smaller than the inner diameter of the diaphragm holder, and the insulating ring is disposed on a flat base. A, an electret in the opening of the insulating ring Step B in which the fixed electrode is arranged with the material surface facing the base side, and Step C in which the gap between the fixed electrode and the opening of the insulating ring is filled with a paste-like bonding material as fixing means The method further comprises at least a step D in which the fixed electrode and the insulating ring are integrated by curing the paste-like bonding material while pressing the fixed electrode and the insulating ring.

According to the fixed pole unit of the present invention, the outer diameter of the fixed pole is not larger than the inner diameter of the diaphragm holder. Therefore, by reducing the stray capacitance and stabilizing the effective capacitance, it is possible to effectively contribute to the improvement of the sensitivity of the condenser microphone.
In the fixed pole unit of the present invention, the fixed pole is fixed at a predetermined position by the insulating ring, and the fixed pole and the insulating ring are integrated by the fixing means so as to form a plane having the same height. Therefore, it is easy to clamp, and an opening can be easily formed regardless of before and after the electret material is attached to the upper surface of the fixed pole even in a large-diameter unit having a large number of holes in the fixed pole. . Moreover, since the fixed pole unit of the present invention can be pressed by a conductive sleeve that is electrically connected to the printed board, electrical connection between the fixed pole and the printed board is easy.
Therefore, according to the fixed pole unit of the present invention, it can be incorporated in the unit case as a constituent member of an electret condenser microphone unit having a structure in which each member is positioned by the pressing force of the folded portion of the unit case. It can be applied to a large-diameter unit having a large number of fixed-pole openings, and the stray capacity of the microphone unit can be reduced.

The method of manufacturing the fixed pole unit according to the present invention includes an insulating ring disposed on a flat base, a fixed pole disposed in the opening of the insulating ring, and an opening of the insulating ring into which the fixed pole is inserted. After the paste-like bonding material is filled in the gap, the bonding material is cured while pressing the fixed electrode and the insulating ring to integrate the two. Therefore, the fixed pole unit in which the outer diameter of the fixed pole is not larger than the inner diameter of the diaphragm holder, and the fixed pole and the insulating ring form a plane with the same height can be easily configured.
Therefore, the fixed pole unit manufactured by the manufacturing method of the fixed pole unit of the present invention has its unit case as a constituent member of the electret condenser microphone unit having a structure in which each member is positioned by the pressing force by the folded portion of the unit case. The microphone unit has a structure suitable for being applied to a large-diameter unit having a large number of openings formed in the fixed pole, and the stray capacity of the microphone unit can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The fixed pole unit of this embodiment is incorporated in the unit case as a constituent member of an electret condenser microphone unit (hereinafter referred to as “microphone unit”), and is opposed to the diaphragm stretched on the diaphragm holder with a gap. The capacitor is disposed between the diaphragm and the diaphragm.
FIG. 1 is a longitudinal side view showing a fixed pole unit according to the present invention. 2A and 2B illustrate the structure of the fixed pole constituting the fixed pole unit. FIG. 2A is a plan view, and FIG. 2B is a longitudinal side view taken along the line II in FIG. 3A and 3B illustrate the structure of the insulating ring constituting the fixed pole unit. FIG. 3A is a plan view, and FIG. 3B is a longitudinal side view taken along line II-II in FIG.
As shown in FIGS. 1 to 3, the fixed pole unit 10 of this embodiment includes a fixed pole 15, an insulating ring 32, and fixing means 30.

  As shown in FIG. 2, the fixed pole 15 uses, for example, a metal disk as a base material, and an electret material 31 is attached to the surface facing the diaphragm to constitute an electret board. The fixed pole 15 can be formed, for example, by punching a metal plate such as brass that can be soldered with a press. On the other hand, the electret material 31 is formed of a polymer film adhered to the surface of the fixed electrode 15 as an electrode plate, for example, by welding or the like. Examples of the polymer film include FEP (fluoroethylene / propylene).

  In addition, the fixed pole 15 is provided with a large number of air holes 10a. The air holes 10a may be formed by pressing the electret material 31 closing the air holes 10a with a press after the electret material 31 is attached to the fixed pole 15 in which the air holes are formed in advance. After the electret material 31 is affixed to the fixed electrode 15 on which no is formed, the vent hole 10a of the fixed electrode 15 and the opening of the electret material 31 may be formed simultaneously by pressing.

As shown in FIG. 3, the insulating ring 32 has an opening 32 a into which the fixed pole 15 is inserted, defines the radial dimension in the unit case, and fixes the fixed pole 15 at a predetermined position. For this insulating ring 32, for example, a PCB (Printed Circuit Board) material which is a material for a circuit board can be used.
In FIG. 3, a land-like first conductor portion 33A is provided in one inner surface of the insulating ring 32, and a land-like third conductor is provided in the inner surface on the other surface. A portion 34A is provided. Further, in FIG. 3, a metal plating 35 for connecting the first conductor portion 33A and the second conductor portion 34A is applied to the inner peripheral wall surface forming the opening 32a of the insulating ring 32. Thereby, it becomes possible to join the fixed pole 15 which is a metal member and the insulating ring 32 which is an insulating member by using cream solder described later as the fixing means 30.
Further, the land-like third conductor portion 33B may be provided in the outer peripheral region on one surface of the insulating ring 32, and the land-like fourth conductor portion 34B may be provided in the outer peripheral region on the other surface. Thereby, the whole height of the fixed pole unit 10 can be made uniform, and a highly accurate flatness can be ensured between the opposing diaphragms. In addition, as each of these conductor parts 33A, 33B, 34A, and 34B, a copper foil can be mentioned, for example, and each said conductor part can be formed with the manufacturing method of a printed wiring board (PCB).

  The fixing means 30 integrates the fixed pole 15 and the insulating ring 32 so that the fixed pole 15 entering the opening of the insulating ring 32 and the insulating ring 22 form a plane having the same height. As the fixing means 30, for example, a paste-like bonding material can be used. More specifically, a paste-like bonding material is filled in the ring-shaped gap formed between the opening 32a of the insulating ring 30 and the outer peripheral surface of the fixed pole 15 disposed in the opening 32a. Then, the bonding material is cured to integrate the fixed electrode 15 and the insulating ring 32. Moreover, as this joining material, what is called cream solder can be mentioned. As a result, even a slight gap between the fixed electrode 15 and the insulating ring 32 can be easily filled, and by heating and cooling to cure the cream solder, the insulating ring 32 and the fixed electrode 15 are reliably bonded. It becomes possible to do.

  As shown in FIG. 4, the fixed pole unit configured as described above is overlaid on the diaphragm stretched on the diaphragm holder with the spacer interposed, as shown in FIG. 4. As shown in FIG. 4, the fixed pole 15 unitized together with the insulation gap 32 has a diameter (outer diameter) D1 of the outer edge portion 15a that is smaller than a diameter (inner diameter) D2 of the inner edge portion 12a of the diaphragm holder 12. (D1 <D2). Thereby, in an assembled state as a condenser microphone unit, there is no overlapping portion between the outer edge portion 15a of the fixed pole 15 and the inner edge portion 12a of the diaphragm support 12, and the condenser microphone unit having high stray capacity and high efficiency. Can obtain a condenser microphone.

Next, a method for manufacturing the fixed pole unit according to the present invention will be described.
FIG. 5 is a manufacturing process diagram schematically showing an example of a method for manufacturing a fixed pole unit according to the present invention.
First, as shown in FIG. 5A, the insulating ring 32 is disposed on the flat base 50. As the base 50, a glass plate can be mentioned, for example.
Next, as shown in FIG. 5B, the fixed electrode 15 is disposed in the opening 32 a of the insulating ring 32 with the electret material 31 forming surface facing the base 50.
Subsequently, as shown in FIG. 5 (c), the gap 3a between the opening 32a of the insulating ring 32 and the outer peripheral surface of the fixed electrode 15 into which the fixed electrode 15 has entered is filled with a paste-like bonding material 30 as a fixing means. To do. As this joining material, for example, cream solder is used. Here, a portion indicated by a dotted circle A in FIG. 5C is enlarged and shown in FIG. In FIG. 6, the bonding material 30 is filled in a gap 3 a formed between the outer peripheral surface of the fixed pole 15 and the metal plating 35 applied to the inner peripheral wall surface of the insulating ring 32.

Thereafter, as shown in FIG. 5 (d), while pressing and pressing the fixed electrode 15 and the insulating ring 32, the cream solder is heated and cooled to be cured, and the fixed electrode 15 and the The insulating ring 32 is integrated by soldering.
And the fixed pole unit 10 can be obtained by removing the base 50 and simultaneously forming the vent hole 10a of the fixed pole 15 and the opening of the electret material 31 by pressing. As described above, the fixed hole 15 in which the vent hole 10a is formed in advance is used, and after the electret material 31 is attached, the vent hole 10a is blocked before or after unitization with the insulating ring 32. It is good also as what opens the electret material 31 which is in a press.

The fixed pole unit 10 configured as described above is incorporated in a unit case to constitute a microphone unit 1 as shown in FIG.
FIG. 7 is a longitudinal side view showing a microphone unit incorporating a fixed pole unit.
In FIG. 7, the microphone unit 1 is configured by housing the following parts in a bottomed cylindrical unit case 11. This unit case 11 has a plurality of holes 11a for introducing sound into the unit. In the unit case 11, a diaphragm 13 stretched by attaching an outer peripheral edge portion to one end face of a ring-shaped diaphragm holder 12 is disposed.

  In addition, the fixed pole unit 10 is arranged with respect to the diaphragm holding body 12 through a spacer 14 that is a ring-shaped member so that the surface on which the electret material 31 is formed faces the diaphragm 13. A gap corresponding to the thickness of the spacer 14 is formed between the diaphragm 13 and the fixed pole unit 10, and the diaphragm 13 and the fixed pole unit 10 constitute a kind of capacitor. Then, as the diaphragm 13 vibrates in accordance with the sound introduced from the hole 11a, the capacitance of the capacitor changes, and the change in capacitance is output as an audio signal. .

  The fixed pole unit 10 is fixed at a predetermined position by an insulating sleeve 16 that defines the radial dimension in the unit case 11. A conductive sleeve 17 made of a conductive material is disposed on the inner peripheral surface of the insulating sleeve 16 so as to be inscribed therein. The rear end surface portion of the conductive sleeve 17 is in contact with a circuit pattern (not shown) formed on the disk-shaped printed circuit board 19, and the open end edge of the unit case 11 is disposed on the peripheral edge portion of the printed circuit board 19. The folded part 11b of the part hits. The folded portion 11b generates a pressing force that directs the printed circuit board 19 forward (upward in FIG. 7). The pressing force pushes the conductive sleeve 17 upward in FIG. Pushed upwards. Further, the diaphragm holding body 12 is pressed against the bottom surface of the unit case 11 via the spacers 14, and the positions of these members in the unit case 11 are determined and fixed.

The conductive sleeve 17 electrically connects the fixed pole unit 10 and the printed board 19. The printed circuit board 19 is provided with a field effect transistor (hereinafter referred to as “FET”) 18 constituting an impedance converter. Some of the terminals of the FET 18 are connected to a predetermined circuit pattern of the printed circuit board 19 by soldering or the like.
As described above, each member including the fixed pole unit 10 and the diaphragm 13 is incorporated in the unit case 11 and constitutes the microphone unit 1 of the electret condenser microphone.

  Thus, in the fixed pole unit according to the present invention, the outer diameter of the fixed pole is smaller than the inner diameter of the diaphragm holder, and the stray capacity of the microphone unit can be reduced. In addition, since the fixed pole and the insulating ring are in the form of a flat plate having the same height, it is easy to clamp, and even a large-diameter unit with a large number of holes in the fixed pole can be easily opened. Can be formed. Moreover, the fixed pole unit according to the illustrated embodiment is pressed by a conductive sleeve that is electrically connected to the printed circuit board, so that the electrical connection between the fixed pole and the printed circuit board is easily achieved. is there.

  Therefore, by providing the fixed pole unit according to the present invention, it is possible to provide an electret condenser microphone unit and an electret condenser microphone with improved detection sensitivity.

It is a vertical side view which shows the Example of the fixed pole unit which concerns on this invention. The example of the fixed pole which comprises the fixed pole unit which concerns on this invention is shown, (a) is a top view, (b) is a vertical side view along the II line in (a). The example of the insulating ring which comprises the fixed pole unit which concerns on this invention is shown, (a) is a top view, (b) is a vertical side view along the II-II line in (a). It is a vertical side view which shows the Example of the fixed pole unit which concerns on this invention with a diaphragm unit. It is a manufacturing process figure which shows simply an example of the manufacturing method of the fixed pole unit which concerns on this invention. It is a vertical side view which expands and shows a part of Example of the fixed pole unit which concerns on this invention. It is a vertical side view which shows the example of the electret condenser microphone unit incorporating the fixed pole unit which concerns on this invention. It is a vertical side view which shows the prior art example of an electret condenser microphone unit. It is a vertical side view which shows the example of the fixed pole in the conventional electret condenser microphone.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electret condenser microphone unit 10 Fixed pole unit 11 Unit case 12 Diaphragm holder 13 Diaphragm 14 Spacer 15 Fixed pole 16 Insulating sleeve 17 Conductive sleeve 18 Field effect transistor (FET)
19 Printed circuit board 31 Electret material 32 Insulation ring

Claims (5)

Built into the unit case,
A fixed pole unit that is disposed opposite to the diaphragm stretched on the diaphragm holder with a gap, and constitutes a capacitor with the diaphragm,
A fixed pole on which an electret material is pasted on the surface facing the diaphragm;
An insulating ring that has an opening into which the fixed pole enters, defines a radial dimension in the unit case, and fixes the fixed pole at a predetermined position;
Fixing means for integrating the fixed pole and the insulating ring so that the fixed pole entering the opening of the insulating ring forms a plane having the same height as the insulating ring;
With
The fixed pole has an outer diameter that is not larger than the inner diameter of the diaphragm holder,
Fixed pole unit characterized by that.   2. The fixed electrode unit according to claim 1, wherein the fixing means is a paste-like bonding material that fills and cures a gap between the fixed electrode and the opening of the insulating ring.   The fixed electrode unit according to claim 2, wherein the insulating ring is provided with metal plating on at least an inner peripheral wall surface forming the opening, and the bonding material is cream solder.   An electret condenser microphone unit comprising the fixed pole unit according to any one of claims 1 to 3. An electret material that is installed in the unit case and is opposed to the diaphragm stretched on the diaphragm holder with a gap therebetween, and forms a capacitor with the diaphragm. A fixed pole to which the fixed pole is attached, an opening into which the fixed pole enters, an insulating ring that regulates the radial dimension in the unit case and fixes the fixed pole in a predetermined position, and the insulating ring A fixing means for integrating the fixed pole and the insulating ring so that the fixed pole entering the opening forms a plane having the same height as the insulating ring, and the fixed pole has an outer diameter Is a method of manufacturing a fixed pole unit having a size equal to or smaller than the inner diameter of the diaphragm holder,
A step A of disposing the insulating ring on a flat base;
In the opening of the insulating ring, the step B of arranging the fixed pole with the electret material surface facing the base side,
A step C of filling a gap between the fixed electrode and the opening of the insulating ring with a paste-like bonding material as a fixing means;
A process D for curing the paste-like bonding material and pressing the fixed electrode and the insulating ring together to integrate the fixed electrode and the insulating ring;
At least in order. The manufacturing method of the fixed-pole unit characterized by the above-mentioned.

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